The present invention relates to a method for forming horizontal buried channels or cavities in wafers of monocrystalline semiconductor material.
In many applications it is necessary to form cavities inside a monocrystalline silicon substrate, for example to obtain suspended masses of microactuators and/or sensors of various types, such as speed, acceleration and pressure sensors, or to isolate electronic components.
Buried cavities can be formed substantially in two ways. According to a first solution, shown in FIG. 1, two monocrystalline silicon wafers 1, suitably excavated and presenting each a half-cavity, are bonded to one another, using an adhesive layer (for example silicon oxide 2), so that the two half-cavities form a buried cavity 3.
According to a second solution, shown in FIG. 2, a monocrystalline silicon wafer 1, suitably excavated and comprising final cavities 4, is bonded to a glass layer 5 (anodic bonding process).
These solutions are costly, have a high criticality and low productivity, and are not fully compatible with the usual technological steps of microelectronics processing. In addition, the buried cavities or channels can be arranged only on a single plane, represented by line 7 in FIG. 3, and it is not possible to form cavities or channels at different heights, as shown in FIG. 4.
The embodiments of the present invention provide a method for overcoming the disadvantages of the known solutions.
According to an embodiment of the present invention, there are provided a method for forming buried cavities in wafers of monocrystalline semiconductor material, and a wafer of monocrystalline semiconductor material. The method includes forming a cavity in a substrate and growing an epitaxial layer on the substrate and in the cavity. In one embodiment, the walls of the cavity are coated with material inhibiting epitaxial growth.